When a sheet of the abovementioned soft material is cut, an edge tool, an ultrasonic cutter, a water jet, or the like has been used conventionally. The use of an edge tool or an ultrasonic cutter has advantages in that the amount of dust generated is small and in that process steps associated therewith, such as waste water treatment, are not required. However, the direction of the edge must be aligned along the moving direction. Furthermore, when a workpiece has a three-dimensional curved surface, more complicated data must be input to a control device for moving the edge tool or the ultrasonic cutter. In addition to this, there is a limit on the control for meeting various requirements on the thickness of a workpiece, the properties of a cut surface, and the like.
Meanwhile, when a water jet is used, work data input to a control device is simplified, but various problems exist. For example, waste water treatment is required, and a workpiece becomes wet. Furthermore, water splashes around the workpiece to deteriorate the working environment, and noise is large. Also, when workpieces are overlapped, it is difficult to cut only one of the workpieces. In addition, the initial cost and running cost are high.
Therefore, in order to solve the abovementioned problems, it has been conceived to mount an ultrasonic cutter on an articulated robot. With such a configuration, the running cost is expected to be reduced, and the restriction on cutting positions is expected to be relaxed. In addition, flexibility in cutting quality can be achieved, and consideration can be given to the environment in terms of drainage, dust, vibration, and noise.
However, in an ultrasonic trimming apparatus having an ultrasonic cutter mounted on an articulated robot, when a cutter blade becomes blunt, the operation must be frequently interrupted to replace the cutter blade. Therefore, a problem exists in that trimming cannot be efficiently performed unless a cutter blade is efficiently replaced.
Furthermore, it may not be publicly known that a cutter blade can be ground by bringing a grinding apparatus having a rotary grindstone close to the cutter blade held attached to a robot. However, when the grinding apparatus is brought close to the cuter blade and the grindstone is rotated, the configuration becomes complicated, and thus it cannot be expected to perform rapid grinding.
Moreover, when a workpiece formed of a soft material is cut, and particularly when the workpiece has a large area, a large number of mechanical clamps are required to secure the workpiece with the clamps, thereby reducing the efficiency. Furthermore, when the outer periphery of the workpiece is trimmed, the clamps are present within the moving range of the cutter blade. Therefore, interference between the cutter blade and the clamps occurs, thereby causing a problem that the working is not completed.
Meanwhile, when a workpiece is formed into a three-dimensional shape, it is important to cut the workpiece with the three-dimensional shape thereof being maintained. Therefore, a configuration has been employed in which a workpiece is cut while being held by a vertical pair of mold jigs which have been worked into the same shape as that of the workpiece. However, in this configuration, two molds, or upper and lower molds, are required, thereby causing a problem of cost increase.
Furthermore, since a six-axis articulated robot has six degrees of freedom, both the position and attitude of a cutter blade can be controlled freely in a three-dimensional space. However, in the structure of the robot, there exists a singular point where the degrees of freedom of motion are reduced to restrict the motion thereof. There are several types of robots including a robot which stops at the singular point, a robot which does not stop at the singular point but passes through the singular point while being operated unstably, and a robot which does not pass through the singular point but is controlled to pass near the singular point. However, in each of these robots, teaching is required to keep away from the singular point, and thus the reduction of the operation speed of the robot and the complication of the teaching are inevitable. Furthermore, in a robot having minimum degrees of freedom, the axes thereof are often fully utilized even in normal teaching, and thus a large amount of time is required for teaching.